Ahh... I see.
Given Rollbit can not share private information here, and you insist that the evidence is nonexistent, that you or your friend have never been warned by Rollbit, I don't think we can get a resolution without someone being a third-party and having an access to those info, in other words: an arbitrator.
Since it's sports-related, I don't think CG will want to handle this. You can try to escalate this to them though, see if they will try to mediate the case and limiting the scope to multi-account detection. Otherwise, I think the other way is only by escalating this to their master license holder. From time to time, Rollbit stated their willingness to cooperate with a mediation of their licensor, and will provide necessary information to them.
However, due to the nature of licensor's mediation that can take weeks, I'm advising you to give CG a shot first, see if they would want to mediate with condition as mentioned above.